package Huihu.src.刷题;

import java.text.DecimalFormat;
import java.util.Scanner;

public class 两点距离 {
    public static void main(String[] args) {
        Scanner scanner=new Scanner(System.in);
        float a=scanner.nextFloat();
        float b=scanner.nextFloat();
        float c=scanner.nextFloat();
        float d=scanner.nextFloat();
        float len=(a-c)*(a-c)+(b-d)*(b-d);
        DecimalFormat df=new DecimalFormat("0.00");
        System.out.println(df.format(Math.pow(len,0.5)));
    }
}
